Microsoft has posted on their Vista website the minimum requirements to run their newest operating system.

The minimum requirements are the following:
Processor: 800 Mhz
RAM: 512 MB
Video Card: DirextX 9 capable card which is able to at least show 800 X 600 resolution
Optical Drive: CD-Rom
Hard Drive: 20 GB that has at least 15 GB of free space for the installation

Note that users cannot run the Aero interface if they have a system that barely pass the minimum specs. There is no news if Vista can be installed on systems which did not meet the specifications above.